Erythritol, a tetra-carbon sugar alcohol (1, 2, 3, 4-butanetetrol, MW: 122.12) is distributed widely in nature. It is found in lichens, mushrooms, fruits, animal semen, lens, and some fermented foods such as wine, Japanese sake, or soy sauce as one of the microbial metabolites. This means that hu-mans have been consuming it unconsciously from ancient times. We tried to establish the mass-production of erythritol by fermentation in order to clarify chemical, physical, and physiological properties that were still unknown, and also to develop its utilization as a food material, as well as an ingredient for chemicals, pharmaceuticals and medicines. Microorganisms having the ability to produce polyols at high yield were screened and isolated from various natural sources by using cul-ture media containing a high glucose concentration. Among them, a few strains were selected as erythritol-producing microorganisms. Some undesirable properties of wild strain, especially insuffi-cient osmo-tolerance in media and vigorous foaming under aerobic culturing conditions were im-proved by UV irradiation and mutagen treatment. Using the mutant strains obtained, large-scale fer-mentation in a reactor tank was tested mainly from the view point of cost reduction. Satisfactory results were obtained in terms of erythritol yield, decrease of coloring materials and by-products, and also aeration conditions. As a consequence, we achieved a manufacturing technology for highly efficient production of erythritol from glucose as a substrate by fermentative process. Since the mass supply of erythritol became possible, its characteristics have been rapidly investigated and clarified. Erythritol is a fine crystal with a sweetness level 75-80% of sugar, heat-stable and less-hygroscopic. It is an extremely low calory sweetner, with an energy value estimated as 0.2 kcal/g. The FDA accepted the application of erythritol as a GRAS material in 1997, and also, the JECFA recognized it as the safest substance, ADI not specified, in 1999. Nikken Chemical Co., Ltd. (part-ner of this research project) launched the commercial production of erythritol and plans to intro-duce industrial uses in the future.